The Russia battalions are explicitly ideologically neo-Nazis and are embraced by Russia and Putin. They don’t mind neo-Nazis; in fact they positively like them! (Which makes the “de-Nazification” casus belli even sillier but that’s neither here nor there.)
The Ukrainian neo-Nazis have never been the majority of their battalion, the battalion has never explicitly been neo-Nazi, the state and the battalion itself have repeatedly rejected Nazism, and reports now are fairly conflicting about how many neo-Nazis remain in its ranks.